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Full Discussion: Read the file line by line and do something with lines
Top Forums Shell Programming and Scripting Read the file line by line and do something with lines Post 303019187 by Don Cragun on Sunday 24th of June 2018 05:44:05 PM
Old 06-24-2018
Quote:
Originally Posted by digioleg54
The last loop doesn't support KSH.
Better is the following:


Code:
for file in $(cat file_name.txt)
do
        print "FILE is $file"
done


Thanks for contribution
Hi digioleg54,
I have no idea what you mean by "The last loop doesn't support KSH." Any POSIX shell and any shell based on Bourne shell syntax does support the while loop MadeInGermany suggested:
Code:
while read line
do
  echo "do somthing with $line"
done < file_name_0.txt

And, it is much more efficient and more likely to work than the loop you suggested above. Your has to start up another shell for the command substitution, run the cat utility to get the contents of file_name_0.txt, and will not work correctly if any filename contained in file_name_0.txt contains any IFS characters (by default, including <space> and <tab>). The code MadeInGermany works correctly in this case while your code does not.

While it is true that the code MadeInGermany suggested will not with if you are using csh or one of its derivatives, the code you suggested will not work with those shells either.
 

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LEARN ABOUT X11R4

break

break(1)                                                           User Commands                                                          break(1)

NAME

       break, continue - shell built-in functions to escape from or advance within a controlling while, for, foreach, or until  loop

SYNOPSIS

   sh
       break [n]

       continue [n]

   csh
       break

       continue

   ksh
       *break [n]

       *continue [n]

DESCRIPTION

   sh
       The break utility exits from the enclosing for or while loop, if any. If n is specified, break n levels.

       The continue utility resumes the next iteration of the enclosing for or while loop. If n is specified, resume at the n-th enclosing loop.

   csh
       The  break  utility  resumes  execution after the end of the nearest enclosing foreach or while loop. The remaining commands on the current
       line are executed. This allows multilevel breaks to be written as a list of break commands, all on one line.

       The continue utility continues execution of the next iteration of the nearest enclosing while or foreach loop.

   ksh
       The break utility exits from the enclosed for, while, until, or select loop, if any. If n is specified,  then  break  n  levels.  If  n  is
       greater than the number of enclosing loops, the outermost enclosing loop shall be exited.

       The  continue utility resumes the next iteration of the enclosed for, while, until, or select loop. If n is specified then resume at the n-
       th enclosed loop. If n is greater than the number of enclosing loops, the outermost enclosing loop shall be used.

       On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words that follow a command preceded by ** that are in the format of a variable assignment are expanded with the same rules as a  vari-
           able  assignment.  This means that tilde substitution is performed after the = sign, and also that word splitting and file name genera-
           tion are not performed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), exit(1), ksh(1), sh( 1), attributes(5)

SunOS 5.10                                                          17 Jul 2002                                                           break(1)
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